DESCRIPTION: The investigators propose to define the molecular mechanisms of T-cell activation and TH-1 cytokine secretion in lamina propria T-cells induced by the antigen-independent CD2 pathway. The nuclear events responsible for TH-1 cytokine gene expression will be examined. Data from the investigator s laboratory have shown a predominance of the CD2 activation pathway, maximized by CD28 coligation, in TCR independent stimulation of TH-1 cytokine secretion from normal lamina propria T-cells. Their analysis of Crohn s disease patients following treatment with anti-TNFalpha monoclonal antibodies demonstrated that mucosal T-cells in vitro become unresponsive to CD2 and CD28 signaling in clinical response of patients. Their research has shown that activated B-cells in the intestinal mucosal are different than activated peripheral blood T-cells. A byproduct of these studies has been the development of a model to study mucosal T-cell regulation. The model, using T-cell activated peripheral blood T-cells, reproduces the functional and biochemical activation state of mucosal T-cells and is a model for investigation of CD2 regulation of mucosal T-cell cytokine genes. Molecular analysis has shown that CD2, but not CD3, ligation of LP-like T-cells is followed by a marked increase in cytokine mRNA production. This response is preceded by induction of AP-1 composed of jun/fos heterodimers. Western blot studies show expression of fos following CD2 ligation. The investigators will use the LP-like T-cell as a system for examination of the hypothesis that induction and/or modification of AP-1 or protein expression with binding of AP-1 and/or NAFT to DNA sequence in their respective promoter regions is central to both IL-1 and interferon-gamma gene expression in lamina propria T-cells following CD2 pathway activation. Their aims are to understand CD2 and/or CD28 regulation of IL-2 and interferon-gamma gene expression in lamina propria T-cells by determining: 1). Whether the augmented IL-2 and interferon-( production seen in lamina propria-like and lamina propria T-cells following CD2 and/or CD28 ligation occurs by increased transcriptional activation and/or mRNA stability. 2). Identifying cis-acting regulatory regions within the IL-2 and interferon-( promotor regions that affect gene transcription following activation of the CD2 and CD28 pathways. 3). The constitutive composition of the jun and jun/fos AP-1 in LP-like and LPT cells and whether activation by CD2 and/or CD28 results in differences in the expression in composition of these dimeric proteins.